Specialist Installer of Solar Photovoltaic and Battery Storage Systems in Oxford and Surrounding Counties

Call us on: 07717 004240

or email enquiries@simssolar.co.uk

Frequently asked questions

Will I still generate electricity if my roof does not face due south?

Yes, in fact, even for roofs facing east or west, predictions indicate that you can still generate up to 85% of what might be achieved from a south facing roof.

What is the optimum angle of panel installation?

It depends on the latitude of the installation, but broadly speaking, you are looking at between 30 and 40 degrees, which fortunately is the angle of a typical UK roof. If you opt for a ground mounted system, then a bit more flexibility is available.

Do you use Google Earth or similar software to design your systems?

There is little that can exceed the benefit of a bespoke house survey. That said, we do use aerial imagery to identify the property while the customer is on the phone which provides useful information regarding roof orientation. We also use manufacturers’ bespoke design tools to help select inverter compatibility with panel choice.

How much electricity am I likely to save?

It depends on your day time habitation of the property. If you are at home during the day, then the saving will be greater than if you are away during the day. If you normally run appliances at night, it may be worth running them during the day when you would benefit from the PV generation (if you are on economy 7 type tariffs you should check which devices are on these circuits as it may be better to use these cost saving tariffs).

There are an increasing number of products entering the market designed to use excess PV electricity generated. Sims Solar can advise you on the different products available and their relative strengths and weaknesses.

How much will I be paid for generating electricity and for exporting my surplus?

It depends on your installation and full estimates will be provided in our quotation. Ofgem maintains a list of relevant tariff rates.

As a rule of thumb, you will generate 980kWh for every 1 kW of installed PV capacity on a south facing roof. The payment you receive will dependent on the tariff rate at the time of application. This income is tax free and index linked to preserve its value.

How do I know how much electricity has been generated?

This is recorded on the Generation Meter, a device that records how much electricity you have generated and will generally be located adjacent to your existing household electricity supply meter.

How much will a typical system cost?

The hardware costs are not fixed and we are typically seeing monthly reductions in panel and inverter costs. For example, a 4kW system costing around £12,000 in December 2011 would now cost from £7,500 (assumes REC 250Wp panels and Fronius TL inverter) (Dec 2012).

What sort of return can I expect?

It depends on the quality of hardware installed, but a return of 8- 10% is not an unreasonable expectation (assumes REC 250Wp panels and Fronius TL inverter) (Dec 2012).

How do I receive my payments for Feed-in Tariff (FiT)?

Once we have installed your system, we will issue you with your Microgeneration Installation Certificate, Proof of Ownership and EPC certificate. We’ll advise you and help you to complete and submit your FiT application form. You will be paid quarterly, providing that you supply Generation Meter readings in line with the schedule sent to you by the FiT licensee (electricity company).

How long do I receive payments for?

For systems installed after 31 July 2012, you will receive FiT and Export Payments for 20 years. For systems installed before this, the duration of payments is 25 years.

What will happen after my FiT payments cease?

You will not receive any direct payments from the FiT licensee (electricity company) but while your system continues to operate, it will generate electricity which you are free to use which will save you money on your electricity bills by reducing electricity bought from the National Grid.

Do I need an EPC certificate to claim the FiT?

If you wish to claim the full rate, you will need a certificate that states that the property meets a Level D energy efficiency performance, otherwise only the lower rate of FiT is available.

If you have had an EPC certificate produced within the last 10 years, perhaps when you bought the property, it should be possible to use this. You can find out whether your property has an EPC certificate by checking on the national EPC database https://www.epcregister.com/home.html . If your property currently does not meet the level D criteria, then it is possible to include the PV installation in the assessment and this may raise your classification to Level D. You are likely to incur a recharge fee, but this is a minor cost.

Sims Solar can advise you on this process.

Can I have an export meter fitted?

Unless your system has an installed capacity greater than 30kWp then no. For systems less than 30kWp you will typically receive a deemed Export Payment of 4.91p per kWh on 50% of what you have generated.

Can I change FiT Licensee (electricity company)?

All of the principal FiT Licensees allow you to change FiT provider, and generally you are required to provide 28 days notice. You can also change whether you opt in or out for export payments, and you are allowed to switch once every 12 months for this.

How do I know if my PV system is working?

This is a test best done during daylight hours. The quickest way is to observe your Generation Meter and observe the flashing red pulse light. The faster it flashes, the greater the production of electricity. If it is not flashing, check the inverter for correct operation.

What maintenance is required?

On a PV system, very little. Depending on your location and nearby trees etc., it may be worth cleaning the solar panels annually. Generally, clean water is sufficient. Specific information on maintenance will be available in the Handover Pack.

On Solar thermal systems, day to day maintenance is minimal, it is worth checking the pressure within the system on a quarterly basis to see if there has been a loss of pressure and the glycol expansion vessel for a release of glycol.

The glycol will need replacing on an interval of 2 – 7 years depending on the frequency of stagnation. Stagnation occurs when the cylinder reaches temperature and the circulation pump shuts down to prevent further heating. If the sun is still shining then the collectors will continue to get hot and at elevated temperatures the glycol will start to degrade and lose its frost protection capabilities.

Is the Handover Pack important?

Yes, it should include all installation critical information so if there is a query with the installation, the query can be readily assessed with all relevant data held on–site.

What is included in the Handover Pack?

We include a range of data including, but not limited to the commissioning certificate, warranty documentation, product and performance literature on panels and inverter, commissioning data, electrical certificate, Part P certificate and Building Control notification, MCS certificate, Structural report and details of maintenance procedures.

We believe that this information is invaluable in the event of a future query.

Do I need planning permission?

The planning regime has been significantly relaxed over recent years. Full details can be found on the Planning Portal and are summarised below. All the following conditions must be observed:

  • panels on a building should be sited, so far as is practicable, to minimise the effect on the external appearance of the building and the amenity of the area
  • when no longer needed for microgeneration, panels should be removed as soon as reasonably practicable

All the following limits must be met for solar panels mounted on a house or on a building within the grounds of a house:

  • panels should not be installed above the highest part of the roof (excluding the chimney) and should project no more than 200mm from the roof slope or wall surface
  • the panels must not be installed on a building that is within the grounds of a listed building
  • wall mounted only - if your property is in a conservation area, or in a World Heritage Site, panels must not be fitted to a wall which fronts a highway

All the following limits must be met for standalone solar panels installations (panels not on a building)

  • only the first standalone solar installation will be permitted development. Further installations will require planning permission
  • no part of the installation should be higher than four metres
  • the installation should be at least 5m from the boundary of the property
  • the size of the array should be no more than 9 square metres or 3m wide by 3m deep
  • panels should not be installed within boundary of a listed building or a scheduled monument
  • if your property is in a conservation area, or in a World Heritage Site, no part of the solar installation should be nearer to any highway bounding the house than the part of the house that is nearest to that highway

Do I need building regulation approval?

As a MCS accredited installer, we need to demonstrate that the roof can take the imposed loads through fitting panels. We use a structural engineer to provide this assessment and we notify Building Control through our scheme administrators. We also make a Part P notification to Building Control for all electrical works.

Are all panels the same?

Sims Solar thinks not. With the reduction in FiT, we have seen a move by some installers toward the budget end of the market. Our concern with this is whether this offers sufficient long term consumer protection should you have need to call upon their warranty. We pride ourselves on using best of breed products with panels from well established companies such as REC and SunPower. These products perform exceptionally well in independent testing and offer exceptional warranties.

Are all inverters the same?

Sims Solar thinks not, the inverter performs the most important role in the whole system, turning DC electricity to useable AC electricity. We use inverters almost exclusively from Fronius and SMA. These two manufacturers provide world class equipment that is reliable, efficient and with excellent technical back up from dedicated UK based helpdesks. We are approved Fronius Service Partners with Fronius recognising our faith in the product and their faith in us as installers.

Are there any components that will require replacing?

A Product failure can never be completely guaranteed against, but careful selection of products at the design stage eliminates the risk as much as is practicable. All panels come with an output guarantee so that any failure of a panel will be addressed under the warranty, but most panel warranties only cover the panel and not incidental costs such as scaffold and labour. One exception is SunPower who also cover incidental costs under their warranty.

It is reasonable to expect to have to replace the inverter at least once in the life of the FiT scheme, All manufacturers offer extended warranties that will provide additional protection in the event of fault. Fronius’ unique Partner Concept allows on-site fault finding and maintenance, minimising down time. Sims Solar is a Fronius Service Partner.

Does Sims Solar provide a warranty?

Yes we do, we offer a 24 month parts and labour warranty and this is backed by an independent insurance policy to provide you long term peace and mind.

What is the warranty on the panels and inverter you use?

The inverters from Fronius and SMA both come with 5 year manufacturers warranties as standard and both can be extended to 20 years in aggregate at additional cost.

The panels from REC and Sunpower have product warranties and performance warranties of up to 25years. The combined product and performance warranty offered by SunPower is world class.

How are panels fixed to the roof?

We use a proprietary mounting system and the roof hook which is used to make the actual physical connection to the roof rafters is selected based upon the tile and roof construction used on the property. All components are stainless steel, offering maximum corrosion resistance and weather proofing.

How do I know if my roof is strong enough to take the weight of the panels?

All MCS accredited installers are required to assess whether the roof is structurally suitable for installation purposes. Sims Solar meets this obligation by using a chartered structural engineer to make this assessment and each assessment includes a visual inspection by the engineer and a bespoke report which we include in the Handover Pack.

We do this to give all parties confidence that there will be no adverse impact from the installation on the roof.

How long does it take to complete a typical domestic installation?

A PV installation will take around one day to complete depending on size and weather conditions. A solar thermal system could take two days depending on whether the hot water cylinder needs replacing.

I have heard that the PV systems cannot be turned off?

During daylight hours DC voltage will be generated at the panels and this cannot be turned off. The inverter and AC side of the electrics can be isolated to allow safe working. All components which could be live during daylight hours are labelled as such. You are at no risk from shock.

What is the effect of shade on the performance of a system?

The effect of shade cannot be under estimated. While bypass diodes provide some protection against leaf matter and bird droppings, they will not address long term shading from chimneys and ultimately the panel will fail to generate. Careful design and the avoidance of shade are the best defence against poor system performance. Multiple tracking inverters and multiple inverters provide another route. Sometimes, less is more when it comes to the question ‘do I squeeze one more panel in?’

Can I take the PV system with me if I move?

Technically yes, but you will not be able to take the FiT with you, so the residual benefit will be only the reduced reliance on the grid for electricity.

Is it worth installing PV systems larger than 4kWp to my house?

n the past the difference between the FiT rate for sub 4kWp systems was significantly more than for systems larger than 4kWp. This is no longer the case and it is certainly worth considering systems larger than 4kWp. But for systems where the inverter can output more than 16A you will need DNO approval to install the system.

Sims Solar routinely installs 4kW+ inverters and we will make all applications to the DNO on your behalf.

What is DNO approval?

Within the National Grid infrastructure, the cables that bring electricity to your house are managed regionally by Distribution Network Operators (DNOs). Legally the local DNO must be contacted and permission obtained to install inverters that export at greater than 16A. This is why many installers will install a 3.6kWh inverter even though you have 4kW of panels on your roof.

Sims Solar can advise on all aspects of DNO approval and the merits of seeking approval.

Am I limited to the number of installations I can have?

No, but you will only receive the maximum eligible rate for the first 25; after that, the FiT rate drops to the middle rate.


“Just wanted to say thank you for such a smooth and professional installation. Throughout the process I found you knowledgeable and trustworthy.”

Mr and Mrs W